Suppression Field hits my fetches
This is a valid point. Perhaps because I think about taxing decks more in terms of different tribes, notably humans, I never thought about using fetch lands in such decks. And with the recent printing of Unclaimed Territory, I just can't help sticking to my guns. With 4x Caverns of Souls and 4x Unclaimed Territory perhaps it is possible to have a more stable five-color humans without fetch lands. Have you thought about this approach?
Shops has a 3-mana land that helps them avoid actually paying for taxing effects, and the best a Human deck with 9 Thorns can do is just stick with creatures as much as possible.
On the bright side, these three mana can be used only to cast artifact spells. With Suppression Field in play Shops will be constrained on resources and may inflict a lot of damage from Ancient Tombs.
Same goes for spot removal in Instant form (Swords, Disenchant, etc). I really need to find those effects on legs in order for it to be included (which sucks, but there are options). If they ever print a Null Rod on legs, it's all over.
With printing of Walking Ballista it is harder to protect life points from creatures, but perhaps Propaganda or Ghostly Prison are still good options (at least for sideboard). Have you tried either of them?
And I wouldn't expect Wizards to print Magus of the Rod after they introduced an artifact themed block.
I also have Windborn Muse as a 1-of, but it hasn't come up in Dredge yet.
I like that the Muse is a 2/3 flying Propaganda. I don't like that she costs four mana and is a spirit. I thought about Peacekeeper
Altogether, I really think the sheer number of blanket hate cards in white, and the number of relevant Humans (And Cats, weirdly) increasing almost every set means the deck should be given a lot more consideration to than it currently is.
Speaking about cats, I found only two white cats that are useful - Leonin Arbiter and Leonin Relic-Warder. Both are Clerics as well. And if Green is something one can splash, Nacatl Savage and Qasali Pridemage can help specifically against Shops.